Observation and measurement of the electroweak W+W+jj process in proton-proton collisions at [square root]s : = 13 TeV with the ATLAS detector = Observation and measurement of the electroweak W^(pm)W^(pm)jj process in proton-proton collisions at [square root]s = 13 TeV with the ATLAS detector

Abstract: Measurements of the electroweak sector of the Standard Model are a way to probe the mechanism of electroweak symmetry breaking at the Large Hadron Collider, and to detect small deviations from the Standard Model predictions, through which the effect of new physics could manifest itself.
In this context the scattering of vector bosons is a key process. In particular the production of W boson pairs is a vital test of the mechanism, since its scattering amplitude would increase at high energies violating unitarity, without cancellations of divergences due to exchanges involving Z or Higgs bosons.
This thesis presents the first measurement with the ATLAS detector at the LHC of the electroweak production of two W bosons with the same electric charge, in the signature with two charged leptons, missing transverse energy and two jets. The process is observed for the first time at ATLAS with a significance of 6.5σ using data recorded in proton-proton collisions at √s = 13 TeV corresponding to an integrated luminosity of 36.1 fb-1, and its cross section in a defined fiducial phase space is measured to be 2.89+0.51/-0.48(stat) +0.29/-0.28(syst) fb.
Among the challenges, the background due to the contributions from opposite-charge di-lepton production processes where the charge of one electron is wrongly reconstructed plays a major role. This thesis details the estimation of this background, whose contribution in the signal region kinematic phase space is determined with a relative uncertainty of 15%. A precise estimation of this background requires a good knowledge of the probability of reconstructing an electron with the wrong charge sign. A measurement of this quantity is presented in this thesis, and the probabilities vary from less than 1% to about 10% for increasing transverse momentum and pseudorapidity of the electrons. Correction factors are provided for the modelling of this effect in simulation, which deviate from unity by up to 30% for wrongly reconstructed electrons, and are determined with relative systematic uncertainties between 2% and 20%.
The contained amount of data limits the precision and sensitivity of the measurement. However, vector boson scattering is one of the most favourable ways to assess clues on the theoretical extension of the SM in a model independent way, and larger datasets at higher energies will make the inner mechanism of the electroweak symmetry breaking and possible new physics more accessible

Object Details

• Alternative title: 13 TeV with the ATLAS detector ; Observation and measurement of the electroweak W^(pm)W^(pm)jj process in proton-proton collisions at [square root]s ; 13 TeV with the ATLAS detector
• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: Universität Freiburg, Dissertation, 2019

Classification and Topics

• Keyword: Higgs-Teilchen

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2020
• Creator: Gonella, Giulia
• Contributor: Jakobs, Karl ; Weiser, Christian ; Albert-Ludwigs-Universität Freiburg. Fakultät für Mathematik und Physik

Further information

• DOI: 10.6094/UNIFR/155037
• URN: urn:nbn:de:bsz:25-freidok-1550370
• Rights: Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 25.03.2025, 1:52 PM CET